Cha'toptcrus Variopedatus. 503 



of the buccal funnel. This has the appearance of a selective response 

 on the part of the cilia. 



The Significance of Mucus. — The presence of mucus in the ciliary 

 currents has been mentioned. Its function in Chsetopterus is 

 probably more complicated than that ascribed to it in corals by Dr. 

 Duerden ('06). I also found that the fine granules of carmine could 

 not be dislodged from the surface of the animal by means of a stream 

 from a pipette, but that they continued towards the mouth in shreds 

 of mucus after they have been dropped upon the animal. Some 

 granules in the mucus passed to the mouth but others were discarded. 

 It is generally true that all of the sand is discarded at the side of 

 the animal. Grains of sand are only occasionally found in the 

 faeces. 



The mucus aids in forming the fsecal masses in the anterior por- 

 tion of the digestive tract. Whether they are formed in the short, 

 glandular diverticulum in the dorsal wall of the esophagTis (Figs. 

 16-18), or in the convoluted portion within the twelfth segment, I was 

 not able to determine. The former is about the same length and 

 diameter as the faecal masses and it may be that the matters accumu- 

 late in this cavity and are there molded into the form of little cylin- 

 ders a millimeter in diameter and six to eight millimeters long. The 

 fa?cal masses discharged by the worms in my aquarium, after the 

 diatoms had not been agitated for twenty-four to forty-eight hours, 

 consisted chiefly of a shell of yellowish mucus with the same form 

 as those which contain diatoms and other organic matter. The 

 walls of these fsecal shells bear several parallel spiral markings that 

 make a single turn. They are probably formed when the little 

 masses are pressed out of the dorsal diverticulum into the lumen of 

 the esophagus. ^ATiether the little masses are formed in the con- 

 voluted portion in the twelfth segment by constriction of its mus- 

 cular wall, or in the dorsal diverticulum, is not apparent from my 

 sections, for it must be determined in specimens killed and preserved 

 on the shoals, because the food passes through the animal so rapidly. 

 Throughout the whole of the intestine of the animal the food masses 

 have the same form and structure. They are dark green, nearly 

 black in color. In the dilated portion of the intestine they are turn- 



